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Water Source Heat Pumping

How to reject heat when there is no ground...
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Jim has noticed that ground source heat pumps are the fashion in low carbon heating and cooling. He thinks this is great for those with some ground and not really practical for those without. In fact the traditional method of rejecting heat into the atmosphere has become impractical for those individuals living in cities (have you ever tried to get planning permission for an external feature...) Currently living in a flat without any ground to dig up and unwilling to pay for the privilege of rejecting heat into the atmosphere Jim needed another (better) solution...

Jim contemplated using the fish tank as a heat sink but could not bring himself to boil the fish during summer... Anyways Jim has decided that water is the answer to this problem since he can reject heat down the drain.... ah actually he can reject heat into the hot water cylinder.

Using the time taken to boil the kettle as a guide Jim reckons there is about 5mins of 2Kw cooling per litre of water. Great Jim reckons the fridge and the air conditioning should be plumbed into the hot water tank...

Happy days...

madness, Jul 03 2009

Like a heat pump water heater? http://www.toolbase...-pump-water-heaters
[ldischler, Jul 03 2009]


       Unless your water source is cooler than the outside air, and stays that way (not the case for a water heater) this is going to be considerably less efficient than an air source unit. If you need the hot water, per [ldischler]'s link it's a good idea, but not otherwise. The advantage of ground loop (or open ground water) is the ground is ~55F, considerably cooler than the air you'd normally be dumping to during cooling season, and warmer than the air you'd be dumping to in heating season.
MechE, Jul 03 2009

       actually no, water/refrigerant AC condensers are very efficient and could easily be included in a supply loop for the hot water heater. I would propose a reservoir system for a moderate volume of water to accommodate the variability in hot water consumption. The outlet water on the water units that I have owned took cold water on the inlet and made thermostatically regulated hot water on the outlet so I imagine you could build a system that basically took care of your hot water needs, in the summer.
WcW, Jul 03 2009

       And water conducts heat about 4 times more efficiently, or "quicker", than air. I reckon it's a fair play to dump heat out of your environ and into your drain, or geyser. But I think this has been proposed on the 'bakery before...
4whom, Jul 03 2009

       Again, I said if you need a hot water heater, it makes sense, if you don't, that's where the problem comes in.


       Heat pumps depend on energy input to create a temperature differential. The larger the differential, the more energy you have to put in, and this is not a linear relationship. Cold water is great, hot water is not. In this system, there is a problem:
Either you are dumping to a finite volume of water, or you are dumping to an infinite volume of water. In the first case it will quickly reach a temperature where it is more efficient to dump to air (I suspect the 125+F of domestic hot water heaters is well past this point on all but the hottest days). In the latter case, you are going to run a lot of water through the pipes, and unless you have a non- drinking water source, the cost of water, and the energy used to purify it will greatly surpass the energy savings from saved versus air.


       If you do have a non-potable water source, this is an open loop or ground water source heat pump, and is thoroughly baked, but that has all its own problems, and is not likely available in an apartment.
MechE, Jul 03 2009

       You might have a non-potable water source, without an open loop or ground water source heat pump.   

       Specifically, if you have a rain water collection system, then that water (until you treat it) is non-potable.   

       Of course, unless you have an infinitely large storage system for the water, you can't simply use it as your heat sink and dump it down the drain... you'll just run out, and then where will you be?   

       However, if you have a sufficient quantity of non-potable water (or if your regular water is sufficiently cheap), you can buy an after market misting device, which sprays water your the air conditioner's condensor. This results in evaporation, which lowers the effective temperature of the condensor.
goldbb, Jul 06 2009

       I should have said continuous flow non-potable water source, I guess.
MechE, Jul 06 2009


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